#include<bits/stdc++.h>

using LL = long long;
const LL inf = 1e9;
const LL P = 998244353;

void solve() {
	int n,m;std::cin >> n >> m;
	std::vector<int> a(n),b(m);
	std::priority_queue<int,std::vector<int>,std::greater<>> q1,q2;
	for (int i = 0; i < n; ++i) {
		std::cin >> a[i];
	}
	for (int i = 0; i < m; ++i) {
		std::cin >> b[i];
	}
	LL need = 0;
	for (int i = n-1, j = m-1; j >= 0; --j, --i) {
		if (a[i] > b[j]) { std::cout << "-1\n";return; }
		else need += b[j] - a[i];
		q1.emplace(a[i]);
	}
	for (int i = n-m-1; i >= 0; --i) {
		q2.emplace(a[i]);
	}
	if (need > n-m) { std::cout << "-1\n";return; }
	std::vector<int> res;
//	std::cout << "size:" << q1.size() << " " << q2.size() << '\n';
	for (int i = 0; i < n-m-need; ++i) {
		if (q2.empty()) { std::cout << "-1\n";return; }
		auto p = q2.top();q2.pop();
		res.emplace_back(p);
		p ++;
		if (p > q1.top()) {
			need -= p - q1.top();
			q1.emplace(p),q2.emplace(q1.top());
			q1.pop();q2.pop();
		} else {
			q2.emplace(p),q2.pop();
		}
	}
	int pointer = 0;
	while (!q1.empty()) {
 		auto p = q1.top();q1.pop();
		if (p == b[pointer]) pointer ++;
		else if (pointer == m || p > b[pointer]){
			std::cout << "-1\n";return;
		} else {
			res.emplace_back(p);
			p ++;
			if (q2.empty()) { std::cout << "-1\n";return; }
			q2.pop();
			q1.emplace(p);
		}
	}
	if (!q2.empty()) { std::cout << "-1\n";return; }
	std::cout << res.size() << '\n';
	for (auto x : res) {
		std::cout << x << " ";
	}
	std::cout << '\n';
}

int main() {
	std::ios::sync_with_stdio(false);
	std::cin.tie(nullptr);

//    clock_t st = clock();
//    std::cout << std::fixed << std::setprecision(12);

//    freopen("test.in", "r", stdin);
//    freopen("test.out", "w", stdout);

	int T = 1;
	std::cin >> T;
	while (T --) {
		solve();
	}

//    std::cout << (double)(clock()-st)/CLOCKS_PER_SEC;

	return 0;
}